Thyristor devices, such as silicon controlled rectifiers (SCRs), may be used as electronic switches in a variety of applications, including, but not limited to power converters, motor drives, pulse power, and the like. In a typical operation, when no electric current (or an insufficient current) is injected into a gate terminal of the thyristor device, then the thyristor device may be in an OFF or blocking state with no current flowing between anode and cathode terminals of the thyristor device. When a sufficient electric current (e.g., above a designated threshold) is injected into the gate terminal, the thyristor device can switch from the OFF state to an ON state, or a conducting state, and the electric current from the anode terminal is conducted through a gate layer and a drift layer of the thyristor device to the cathode terminal.
A class of thyristor devices called light triggered thyristors can be optically switched to the conductive state by applying light to the gate pad which then generates an electric current, through a photodiode effect, which is injected into the thyristor gate. The light-generated current can be supplied to the gate terminal to switch the device to the conducting state. Using a light source to switch the state of the thyristor device can be useful in many high voltage applications because the light source can be isolated from the thyristor terminals (anode or cathode). This is beneficial because the gate terminal is decoupled from the high voltage terminals (anode or cathode), and can allow multiple devices to be strung (e.g., connected) in series without additional circuitry. Additionally, the gating of many thyristors in a series or parallel string may occur simultaneously and accurately.
However, in some high voltage applications requiring kilovolts, and/or very high anode-cathode currents, the gate current required to turn-on the thyristor devices can be significant (e.g., a few amperes). This current level may be much larger than what can typically be generated by existing light sources. As a result, the use of optically controlled thyristor devices may be limited to lower voltage and current applications. It would be beneficial to have a thyristor that is optically triggered and that can operate in high voltage, high current applications.